Computers are cheapest on Mondays because manufacturers apply their rebates early in the week. This means online retailers can purchase computers for less and pass the savings on to you. This is not the case with every manufacturer, but Dell and Sony are among the companies that do this with their computers.

Mondays are also cheap days for TVs (and Tuesdays aren't bad either) not only because of the same rebate situation, but because big sales days tend to be earlier in the week. This gives retailers an opportunity to draw more buyers in, and lower prices are a good way to do that. Cameras and video games also benefit from lower prices earlier in the week for the same reasons.

Major appliances tend to be cheapest on Sundays because that's when the majority of people are searching for them. Washers, dryers, ovens, microwaves, refrigerators, and more are all Googled like crazy at the end of the week, so online retailers adjust their prices to draw people in.

Jewelry prices drop down on Wednesdays because that's when searches take place as well. Apparently women tend to shop online most often in the middle of the week, and since women are the target market for most jewelry we see price drops to help attract buyers.

Books are at their lowest on Saturdays, although there isn't a solid reason why. Perhaps people read more on Saturdays, or at least thing they should be reading more when the weekend finally rolls around.

For more information on why these prices fluctuate online on certain days, plus lots of pretty graphs, check out the full post over on Extrabux.